The present invention is directed to a device for folding the flaps of a box blank and maintaining the folded flaps. The device has upper and lower side conveyors, a central lower conveyor, and an arrangement for folding composite front and rear flaps and also simple flaps. The present invention is also directed to a device for maintaining the simple or composite flaps in their folded positions for a box blank which are called boxes with six glue points by persons skilled in the art.
One of the known devices for the folding of the front flaps of a box is made of several hooks positioned along the running direction of each of the box flaps. These hooks are identical to the ones described in Swiss Pat. No. 383 140 corresponding to U.S. Pat. No. 3,285,144 and engage the front flap and folds it over as the blank moves under the hooks. The folding of the rear flap is also performed with a device provided with hooks which are rotated and hit a rear part of the blank. The device for folding the rear flaps is described in Swiss Pat. No. 464 671. The folding of the rear and front flaps occurs during the linear movement of the blanks which are driven by a lower and upper conveyor arrangement so that they do not jeopardize the pulling down of the flaps during the folding operation. For this folding of the front and rear flaps, the hooks of the folding device are cooperating with an upper member, usually a folding screw or, in more elaborate constructions, a set of rods with varying flexibility arranged side-by-side in the same plane, which can change form with regard to the dimensions of the flaps to be folded. Unfortunately, such an upper member, however, shows an important drawback when the production speed of the folder-gluer has been increased. The part of the flap of the box blank touching the upper members are running at a relatively high speed, whereas the element of this upper member is held in a fixed position. It doesn't matter, as long as the machine doesn't work at high speed, because the friction between the flaps and the upper member does not affect the folding condition. These things are different as soon as a high speed production is required, for example, with blanks running at a speed of 300 to 400 m/minute. The running tests have shown that this type of upper member is not appropriate as the friction and the hitting of the flaps on the elements of the upper member would cause damage or tear up the box blank which is to be folded.